In a railway vehicle such as a Shinkansen bullet train, during running, vibration acceleration in motion such as vertical motion, lateral motion, rolling and yawing is imposed and a vibration is generated. Therefore, in a railway vehicle, a vibration suppression device for suppressing various vibrations is mounted. As a damping force generation mechanism of the vibration suppression device, an air cushion, a fluid pressure damper utilizing pneumatic pressure or hydraulic pressure, an actuator of fluid pressure type such as pneumatic pressure or hydraulic pressure as a drive source, an electric actuator with electric power as a drive source, and the like are used. These are disposed between a bogie truck and a vehicle body of the railway vehicle.
In the actuator among these damping force generation mechanisms, a main body is coupled to either the bogie truck side or the vehicle body side, and a movable rod is coupled to the other side. With the rod being extended or retracted in association with a generated vibration, the actuator exerts to vibrate the vehicle body and at the same time, to adjust a damping force of the actuator itself to attenuate the vibration. At this time, in the fluid pressure type actuator, a rod (piston rod) is arranged inside a cylinder on the main body side, and by controlling a supply amount (sealed amount) of compressed air or oil into the cylinder, the rod is extended and retracted. In the electric actuator, a rod is arranged in a coaxial manner with a main shaft of an electric motor on the main body side via a ball screw mechanism, and by controlling a rotation angle of the electric motor, rotation motion of the electric motor is converted into linear motion and the rod is extended and retracted.
In the vibration suppression device using the actuator, a failure that extension/retraction motion of the actuator is disabled (hereinafter, this failure will be referred to as “seizing”) can be generated. The seizing of the fluid pressure type actuator is generated in the case where a port for supplying the compressed air or the oil to the cylinder remains opened or closed due to some troubles, or the like. The seizing of the electric actuator is generated in the case where the ball screw mechanism gets stuck by a foreign substance, or the like.
In the case where the seizing is generated in the fluid pressure type actuator, the actuator is brought into the state of having lower rigidity to allow extension/retraction of the rod a little owing to a compression characteristic of the fluid retained in the cylinder. Meanwhile, in the case where the seizing is generated in the electric actuator, the actuator is brought into the state of having higher rigidity substantially which does not allow the extension/retraction of the rod. In any of the actuators, generation of the seizing does not immediately cause fatal damage to running safety and riding comfort but undeniably deteriorates the riding comfort. Particularly, in the electric actuator to be brought into the state of higher rigidity in accordance with the generation of the seizing, the level of degradation of the riding comfort is intensified.
Therefore, in the case where the actuator is seized, there is a need for repairing or replacing the actuator. As a technique in the background art for this demand, for example, PATENT LITERATURE 1 and 2 disclose a technique in which when a railway vehicle is out of service, an actuator is intentionally activated to vibrate a vehicle body, the vibration acceleration of the vibrated vehicle body is detected by an acceleration sensor, the detected vibration acceleration is compared to a reference value, and in the case where the vibration acceleration is smaller than the reference value, it is diagnosed that the actuator is in a fault condition.